Abstract: Femtocell is a promising technology to enhance indoor coverage and system capacity. However, the interference impairs greatly the network performance for spectrum-sharing OFDMA femtocell networks. This paper investigates a power control scheme for the uplink transmission of spectrum-sharing femtocell networks based on cooperative game theoretic framework. Taking into consideration both user fairness and network efficiency, a cooperative Nash bargaining power control game model is formulated, where interference power constraint is imposed to protect cellular users transmission, and minimum Signal-to-Interference-plus-Noise Ratio (SINR) requirements are employed for femtocell users. Then a Kalai-Smorodinsky (KS) bargaining solution is developed, which is a Pareto-optimal solution to the problem. Simulation results show that the proposed algorithm not only maintains fairness among femtocell users and guarantees the minimum SINR requirements of all femtocell users, but also improves the spectrum efficiency.